1. Field of the Technique
The present technique relates to a virtual tape-library apparatus that is between a host computer and a tape library apparatus, and stores tape data received and transmitted between the host computer and the tape library apparatus.
2. Description of the Related Art
FIG. 1 is an explanatory diagram of a conventional virtual library system.
A virtual library system 101 connected to a host computer 201 has a virtual library apparatus 102 and a tape library apparatus 103. The virtual library apparatus 102 has a cache disk 111.
Further, the tape library apparatus 103 has a storage medium 121 for the virtual library apparatus 102 and an external storage medium 122.
The virtual library system 101 virtualizes a tape volume, and emulates the tape volume on the cache disk 111. Therefore, the virtual library system 101 does not have the concept of medium discharge provided for the conventional tape library apparatus 103. Then, the virtual library system 101 has an export function/import function, as a system for discharging the stored logical volume and for realizing an operation of external storage.
With the export function, a plurality of logical volumes stored in the storage medium 121 for the virtual library apparatus 102 are copied in a lump to the external storage medium 122 having a large capacity. The copied external storage medium 122 is externally extracted and is stored to an external archive.
With the import function, the external storage medium 122 externally-extracted from the virtual library system 101 with the export function is input to another virtual library system 101, thereby restoring the logical volumes.
In general, the logical volume in the virtual library system 101 is stored to the storage medium 121 for the virtual library apparatus 102 with a large capacity.
With export function/import function, upon executing the copying/restoring operation of the logical volume, the determined logical volume is copied to the cache disk 111 once. Further, at the import time, the logical volume is copied to the storage medium 121 for the virtual library apparatus 102 from the copied cache disk 111 and, at the export time, the logical volume is copied to the external storage medium 122.
As the cache disk 111, a disk array device is used and the cache disk 111 comprises a plurality of disk volumes. Further, the disk volumes are divided into a plurality of logical volumes. If the logical volume is assigned to the disk volume once, it is not subsequently changed.
Therefore, in frequent access to the logical volumes assigned to the same disk volume, the load is large. Further, access performance of the cache disk 111 deteriorates, thereby causing a case in which a normal processing capacity is not exhibited.
In particular, with the export function/import function, a large number of logical volumes are read and written once and the processing capacity is thus extremely reduced. FIG. 1 shows an example of causing the large load in a disk volume A in the export processing.